TL;DR: Researchers reported silicon-doped alpha-phase aluminum gallium oxide films with bandgaps above 7.0 eV, the widest-bandgap semiconductor described to date.

A 7-eV semiconductor enters the record books

On 07 October 2026, the journal Nature published a report titled A 7-eV bandgap semiconductor based on silicon-doped α-(AlxGa1−x)2O3, by Jacob Steele, Debaditya Bhattacharya, Kazuki Nomoto and colleagues. According to Nature, the team grew silicon-doped α-(AlxGa1−x)2O3 films by suboxide molecular-beam epitaxy with bandgaps exceeding 7.0 eV. According to Nature, those films surpassed cubic boron nitride, described in the paper as the next-widest-bandgap semiconductor known. A companion News & Views article in Nature titled Semiconductors pushed into insulator territory, by Hironori Okumura, described the result as a semiconductor with the biggest bandgap recorded so far.

The central claim is narrow and concrete. According to Nature, the films combine a bandgap above 7.0 eV with controlled silicon doping and room-temperature conductivity. According to Nature, in the colossal-bandgap regime above 6 eV, the silicon-doped films showed room-temperature conductivities over 100 million times higher than all previous reports. According to Nature, the team used the films to fabricate a Schottky diode and a field-effect transistor called the AlphaFET with colossal-bandgap channels.

Why bandgap matters for power electronics

According to Nature, wider-bandgap semiconductors allow higher efficiency and power density in rectifying power electronics. According to Nature, the Baliga figure of merit is proportional to Eg to the power 5.5. That relationship is cited in the paper with references to work by B. J. Baliga and to an analysis of critical electric field versus semiconductor bandgap by Slobodyan and colleagues.

The companion News & Views article titled Semiconductors pushed into insulator territory gives the textbook framing. According to that assessment, semiconductors are materials that have an electrical conductivity between that of a conductor and an insulator. According to that assessment, the properties of a semiconductor are governed, in part, by its electronic bandgap. According to that assessment, the bandgap is the energy needed to promote an electron to a conducting state.

According to that assessment, semiconductors with large bandgaps are sought for electronic devices that must operate at high voltages or high temperatures. That demand is the context for the new oxide result. According to Nature, increasing demand for wider-bandgap semiconductors has led many materials previously considered insulators to emerge as useful semiconductors. According to Nature, that list includes GaN, SiC, AlN, Ga2O3 and GeO2. According to Nature, that transition followed decreasing defect densities and finding appropriate dopants.

An analysis published by Applied Tech Insider under the title 7-eV Oxide Semiconductor Pushes Power Electronics placed the same tradeoff at the center. According to Applied Tech Insider, a 7-eV bandgap sits in a range many engineers would associate with insulating behavior, not useful semiconductor conduction. According to Applied Tech Insider, Nature published the paper on Oct. 7 alongside a News & Views article describing the result as a semiconductor with the largest recorded bandgap. According to Applied Tech Insider, the evidence does not mean commercial 7-eV power switches are ready.

What the team actually grew

According to Nature, the material is silicon-doped α-(AlxGa1−x)2O3. The notation describes an alloy of aluminum and gallium in the alpha phase of gallium oxide chemistry, with silicon added as a dopant. According to Nature, the films were grown by suboxide molecular-beam epitaxy. That growth approach is identified in the paper title and abstract as the method that produced the above-7.0-eV films.

According to Nature, the study reports bandgaps exceeding 7.0 eV. According to the companion News & Views article titled Semiconductors pushed into insulator territory, the reported bandgap exceeds 7 electronvolts. According to that assessment, the demonstration pushes semiconductors into a regime that has long been reserved for insulators.

According to Nature, the result surpasses cubic boron nitride. According to Nature, cubic boron nitride was the next-widest-bandgap semiconductor known. The paper supports that comparison with references to ultraviolet spectra of cubic boron nitride, ultraviolet luminescence spectra of boron nitride single crystals grown under high pressure and high temperature, and determination of optical band-gap energy of cubic and hexagonal boron nitride using luminescence excitation spectroscopy.

According to Nature, the authors define a colossal-bandgap regime above 6 eV. According to Nature, in that regime the silicon-doped α-(AlxGa1−x)2O3 films have room-temperature conductivities over 100 million times higher than all previous reports. The paper links that benchmarking statement to prior work on metalorganic chemical vapor deposition growth of silicon-doped α-(AlGa)2O3 on m-plane α-Al2O3 substrates.

Doping is the hard part

According to Nature, the distinctive ability of semiconductors to have conductivities controllably modulated over orders of magnitude by equilibrium doping methods becomes increasingly elusive as bandgap increases. That observation explains why a wide bandgap alone is not sufficient. According to Nature, many wider-bandgap candidates were once treated as insulators. According to Nature, GaN, SiC, AlN, Ga2O3 and GeO2 became useful semiconductors after defect densities were reduced and appropriate dopants were found.

The new work follows that pattern. According to Nature, silicon is the dopant in the α-(AlxGa1−x)2O3 films. According to Nature, the silicon-doped films retained high room-temperature conductivity in the above-6-eV range. According to Nature, that conductivity was more than 100 million times higher than all previous reports in that regime. The comparison establishes controlled doping, not only optical transparency or crystal structure, as the advance.

The News & Views article titled Semiconductors pushed into insulator territory frames the same point as a boundary crossing. According to that assessment, a material previously assumed to be an electrical insulator has been shown to be a semiconductor. According to that assessment, the new semiconductor has potential uses in electronics and optics. According to that assessment, semiconductors are ubiquitous in modern technology, enabling the controlled flow of electricity in everything from solar cells to smartphones.

According to Applied Tech Insider, raising the bandgap is not enough without controlled doping, contacts, patterning and incorporation into working device structures. According to Applied Tech Insider, the alloy notation matters because the material is not ordinary silicon or a familiar commercial wide-bandgap compound. According to Applied Tech Insider, it is an oxide semiconductor system in which aluminum and gallium are combined in the alpha phase, with silicon used to introduce n-type conductivity.

Two early devices: a diode and the AlphaFET

According to Nature, the researchers fabricated a Schottky diode and a field-effect transistor with colossal-bandgap channels. According to Nature, the transistor is called the AlphaFET. The paper presents electrical characteristics of the diode and the transistor in dedicated figures.

According to Applied Tech Insider, the work included early devices such as a Schottky diode and an AlphaFET. According to Applied Tech Insider, those demonstrations matter because they show semiconductor behavior in device-relevant structures, not only optical or materials characterization. According to Applied Tech Insider, a Schottky diode is an important test of rectification, contacts, leakage and barrier behavior. According to Applied Tech Insider, a field-effect device is an important test of channel modulation and device processing.

According to Applied Tech Insider, neither device proves that the material is ready for high-volume power modules, automotive qualification, grid deployment or aerospace reliability programs. According to Applied Tech Insider, the useful interpretation is narrower. According to Applied Tech Insider, the researchers have shown that conductivity and device behavior can be achieved above the 7-eV bandgap threshold in this oxide system.

According to Nature, the channels in both devices use colossal-bandgap material. That detail connects the film result to device operation. According to Nature, the films and devices together support development of colossal-bandgap electronics. The paper does not present the diode and transistor as commercial products.

Sapphire changes the cost and scale story

According to Nature, the α-(AlxGa1−x)2O3 films and devices use sapphire. According to Nature, sapphire is an abundant, inexpensive substrate with excellent quality that is produced at massive scale. According to Nature, that substrate choice facilitates development and adoption of colossal-bandgap electronics.

That point is central to the paper's claim of practical relevance. According to Nature, the achievement breaks the trend of increasing synthesis difficulty, cost and small size of ever-wider-bandgap semiconductors. According to Nature, diamond and cubic boron nitride are examples of that trend. In other words, wider bandgaps have historically meant harder growth, higher cost and smaller crystals.

According to Applied Tech Insider, that framing is the story for power electronics. According to Applied Tech Insider, the tradeoff involves bandgap, conductivity, substrates, fabrication and manufacturability. According to Applied Tech Insider, the demonstrated devices are still early material proof points. The substrate therefore matters as much as the bandgap number because it affects how other groups might reproduce and extend the work.

The paper cites earlier crystal-orientation work on ultrawide-bandgap 5.4- to 8.6-eV α-(AlGa)2O3 on m-plane sapphire. It also cites prior epitaxial growth of α-(AlxGa1−x)2O3 by suboxide molecular-beam epitaxy at 1 micrometer per hour. It cites silicon-doped (AlGa)2O3 growth on a-, m- and r-plane α-Al2O3 substrates by molecular beam epitaxy. It cites conductive silicon-doped α-(AlxGa1−x)2O3 thin films with bandgaps up to 6.22 eV. Those references place the above-7.0-eV result in a sequence of sapphire-based oxide epitaxy studies.

How this compares with diamond and boron nitride

According to Nature, diamond and cubic boron nitride illustrate the prior cost-size-difficulty trend for ever-wider-bandgap semiconductors. According to Nature, the new films break that trend because they use sapphire produced at massive scale. The contrast is explicit in the abstract: excellent-quality, inexpensive, abundant sapphire versus small, difficult, costly crystals.

According to Nature, cubic boron nitride was the next-widest-bandgap semiconductor known before this report. According to the News & Views article titled Semiconductors pushed into insulator territory, the new semiconductor has the biggest bandgap recorded so far. The two statements together define the record claim. The paper volume is identified in the News & Views references as Nature 658, pages 623-628, in 2026.

The historical context includes other ultrawide-bandgap substrates. The paper cites work on transistors on ultrawide bandgap single-crystal AlN substrates. It cites a roadmap for ultraviolet emitters. It cites reviews on dopants and defects in ultra-wide bandgap semiconductors. It cites histories of semiconductors, silicon carbide power devices and AlGaN/GaN high-electron-mobility transistors. Those citations do not change the core comparison. According to Nature, the above-7.0-eV silicon-doped oxide now sits above cubic boron nitride on bandgap.

Who reported it and where to find it

The Nature article lists Jacob Steele and Debaditya Bhattacharya as equal contributors, with Kazuki Nomoto, Naomi A. Pieczulewski, Preston Sorensen, Viet-Anh Ha, Nick Pant, Ihit Shukla, Shaon Das, Ufuk Kilic, Madhav Ramesh, Feliciano Giustino, Baishakhi Mazumder, M. K. Indika Senevirathna, Michael D. Williams, Mathias Schubert, David A. Muller, Huili G. Xing, Debdeep Jena and Darrell G. Schlom among the authors. A visualization record identifies the Department of Materials Science and Engineering at Cornell University in connection with the author list. The article carries the digital object identifier 10.1038/s41586-026-11085-3.

The companion piece titled Semiconductors pushed into insulator territory was written by Hironori Okumura. That author is identified as being at the Institute of Pure and Applied Sciences, University of Tsukuba, Ibaraki, Japan. It was published as News & Views on 07 October 2026. It references Steele and colleagues as Steele et al. in Nature 658, 623-628.

According to Nature, the data supporting the results are available in the paper, its Extended Data figures and the Supplementary Information. According to Nature, the raw data used to create figures are available upon request to the corresponding author. The article was published online on 07 October 2026.

What remains a laboratory result

According to Nature, the work reports films and two device types. According to Nature, it does not report a commercial power module. According to Applied Tech Insider, commercial 7-eV power switches are not ready. According to Applied Tech Insider, the demonstrated devices are early material proof points rather than finished inverter components.

According to Applied Tech Insider, silicon carbide power electronics are relevant context because the Department of Energy describes SiC as able to tolerate higher temperatures and voltages than silicon, switch faster and reduce conversion losses. According to Applied Tech Insider, those properties matter in equipment that converts electricity into the right voltage, current or frequency. According to Applied Tech Insider, examples include grid converters, electric-vehicle chargers, traction inverters, industrial drives, renewable-energy interfaces, aerospace power systems and high-temperature electronics.

That context explains interest without overstating readiness. According to Applied Tech Insider, ultra-wide-bandgap materials extend the logic of silicon carbide. According to Applied Tech Insider, a larger bandgap can in principle support higher critical electric fields, thinner drift regions, lower resistance at a given blocking voltage and operation where silicon would be inefficient or impractical. According to Applied Tech Insider, the same gap that supports high breakdown strength can make it hard to generate enough mobile carriers for low-resistance conduction. The reported advance is therefore described as pushing the conductivity and device-demonstration boundary, not delivering a qualified product.

Sources referenced